It depends on who you ask, as some people will quarantine for up to 3 months. In my quarantine I always run copper, and then when I add fish to my dt I treat with prazi even if no symptoms are shown. The copper kills things like velvet and ich, and i do it in qt because there aren't any inverts in there, then I treat with prazi for about a week in my dt and that will deal with most parasitic diseases. I've noticed more so with saltwater fish that diseases can go without symptoms or lay dormant for weeks to months before popping up out of nowhere, most of the time its because something with the water quality changed and then out of nowhere ich arises. Qting for longer should help a lot with preventing disease. Whenever getting a new fish always assume it is diseased.

